Bypass standby switch

[jimmys]

setting up curing chamber for salami etc. wired up humidifier to humidity controller. however, the humidifier has a standby mode so that i need to push the button to switch on. any way of bypassing this so that when get power from controller it switches on?
thanks, James

 

[KrisBlueNZ]

Hi James and welcome to Electronics Point

The simplest solution would be to short out the Standby button, but the humidifier may require a discrete button-press, and may ignore the button if it's forced ON. But you can easily test it to find out - just hold the button in, then switch on the power to the humidifier, and keep holding the button.

If the humidifier starts up, you've solved your problem - just bridge the two connections on the button. Or preferably, make some reversible modification to keep the button pressed - maybe jam a toothpick down the side of it, if it's recessed, so that it's stuck in the 'in' position.

If the humidifier doesn't start up with the button held in, you will need a circuit that is powered in parallel with the humidifier, that waits for a few seconds, then generates a closure on a relay contact which you would wire across the pushbutton.

This closure may need to be brief (i.e. press then release the button) or the humidifier may accept a continuous closure. Again you can test this by powering up the humidifier, then pressing and holding the button. If it starts up and keeps running, even with the button held in constantly, then you just need a delayed closure. If you have to press the button then release it before the humidifier starts up, you need a delayed brief closure.

Either of those options can be done with a fairly simple circuit, powered from a low-voltage wall wart.

If you can upload a few photos of the inside of the humidifier, we may be able to suggest a simpler solution.

Is it possible that the humidifier has a programmable option to make it turn ON as soon as it receives power?

 

[jimmys]

Hi Kris, Thanks for that. Tried the "holding on button on" and it works. So that won't cause any problem if held in the whole time? Attached a couple of pics - the centre button is the ON/OFF with others being: timer, ion, strength of vapor dispersal.

 

[KrisBlueNZ]

Hi Kris, Thanks for that. Tried the "holding on button on" and it works. So that won't cause any problem if held in the whole time?

I don't know. Have a look through the manual and see if it mentions any special function that you can get by holding the button down.

I would just jam a toothpick in there, and try it out manually and see whether it starts up each time you plug it in, and seems to work normally for a reasonable amount of time.

Also, does it do anything after you turn it off with the pushbutton? Pulling the plug without turning it off with the button and waiting a while may prevent it from doing some important things. See whether the manual says anything about leaving it plugged in for a certain length of time after you turn it off with the button.

 

[jimmys]

hi again, no luck from the vendor regarding a programme bypass. The options are: a) pay the postage and send it back to buy a much smaller one (not great) that has no standby, b) with your help, have a crack at some electronic bypassing action. What do you think?

 

[jimmys]

by the way, the toothpick thing doesnt really keep the button in.

 

[KrisBlueNZ]

hi again, no luck from the vendor regarding a programme bypass. The options are: a) pay the postage and send it back to buy a much smaller one (not great) that has no standby, b) with your help, have a crack at some electronic bypassing action. What do you think?

I'm not sure what you're asking. I thought you had the problem solved when you said

Tried the "holding on button on" and it works.

If the toothpick doesn't work, there's probably some other way to hold the button in without opening it up and soldering a link across it. Can you put a loop of elastic around the top of it, with something between the elastic and the button, or something like that? Use your imagination.

So you tried holding the button down continuously (or jamming a toothpick in it, or something similar), then plugging it in, and it worked? And it kept working until you unplugged it? If so, that's all you need to do.

My other suggestion was that it may need to be turned off by the button, if it does some kind of wind-down process which still requires mains power. So, check the manual for a warning about leaving it plugged in for a certain amount of time after putting it into standby. If that is a requirement, then you shouldn't be just powering it off by removing the mains power with the timer.

 

[jimmys]

Have had a good go at trying to keep the button in without luck - just can't seem to get as much pressure as I can with my finger. So, is it possible to bridge the two connections?

 

[KrisBlueNZ]

From those photos, it looks like you could slide something (e.g. a piece of cardboard, or a toothpick or a matchstick) in between the bottom of the white plastic stalk from coming down from the piece that you press, and the black plastic actuator on the top of the little tactile pushbutton that's mounted on the circuit board.

If that doesn't work, then yes you can bridge the terminals. It looks like those tactile switches have four terminals. Normally, the two terminals on each side are internally connected together, and so are the two on the other side, so you need to bridge from one side to the other.

Get a piece of hookup wire with the insulation removed and the cores twisted together, and solder it to one pad (either pad) on one side, then to one pad on the other side. If there are exposed tracks that it has to cross, use insulated wire.

 

[jimmys]

hookup wire 0.12mm?
dont have soldering iron so what size should i buy? would this fix affect the low water shutoff mechanism?
have attached pics of front of board with on/off switch, and two pics of terminals i think you are suggesting

 

[KrisBlueNZ]

Yes, 0.12 mm would be fine. It doesn't need to carry much current. And a cheap 30W soldering iron, and standard tin-lead solder about 0.8 mm diameter would be good.



You can connect the wire straight across the two connected switch terminals, with a wire in position A, or position B, which is electrically the same and only needs a short wire. You might even be able to connect those two terminals together with a big blob of solder and no wire.

But it would be a lot cheaper to jam a little wooden wedge in there. I would try all of the simple, cheap solutions first.

 

[jimmys]

so the far left circled, and upper right circled are on same circuit? i've attached pic of what that upper circled terminal is on front side. is it ok?

 

[KrisBlueNZ]

Yes and yes. I've outlined, in red, the copper area (lighter green colour) to show how the bottom left circled point connects to the top right circled point.

 

[jimmys]

Ok - just got back from town. REady to go. Here goes ...Thanks for all your help

 

[jimmys]

We have lift off. I'm feeling pretty pumped - love learning a new skill i.e. soldering. Helpful dude in town from AutoPro who just gave me some speaker cable. Not the prettiest solder but it is working as desired. You are a champ Kris for teaching me a bit of stuff and giving me options. If only I could post you some chorizo or salami when I've finished curing my first batch. Thanks mate.
Regards
James

 

[KrisBlueNZ]

Good one James